Semiconductor devices, electronic devices, and photonic-crystal and other optical devices are fabricated by forming submicrometer (around 0.1 μm to 1 μm) precision pattern structures on a face of a semiconductor wafer and the like. In semiconductor quantum devices, an array of ultra-fine particles or lines measured in nanometers, which are called quantum dots or quantum wires, is formed on a surface of a substrate. The size and surface roughness of the relief structures (pattern structures, structures formed by an array of ultra-fine particles, etc.) formed on those devices are important factors that affect the performance of the devices. Therefore, high precision is essential for the formation of the relief structure.
The precision of the relief structure depends on the precision of a film formation processes, an etching processes, and other fabrication processes. It is not easy to form a relief structure with a precision of up to a few nanometers. Generally, in these devices fabricated through the film formation process, etching process, and so on, a great number of chips are formed on the surface of a semiconductor wafer. However, it is difficult to form uniform relief structures across the entire surface of the semiconductor wafer. To solve these problems, a process to improve the precision of the structure (such as smoothing) is conducted after the relief structure is formed.
One smoothing technology disclosed in International Publication Number WO2005/031838 (Patent literature 1) smoothes out side walls of a pattern structure and the like by irradiating it with a gas cluster ion beam.